The present invention relates to a flexible coupling, particularly useful for a double mass flywheel for internal combustion engines, which damps rotary oscillations dependent upon load conditions in the coupling.
A coupling of this type is known from Federal Republic of Germany Patent 2,848,748. (and corresponding U.S. Pat. No. 4,351,167) The coupling includes two coupling halves relatively rotatable about a hub. The first coupling half includes two axially spaced apart outer disks which are bridged radially outwardly to define an enclosed inner space for containing a damping fluid. One or a plurality of disks are connected with the second coupling half and are disposed in the inner space in the damping fluid. A flexible connection is provided between the first and second coupling halves, that is between the disks of the first coupling half and the disks of the second coupling half. In addition, relative motion between the coupling halves should be damped so that they move together and also in order to avoid oscillations. In general, there are displacement chambers defined in the disks with one circumferential side of the chamber being defined by one disk and the other circumferential side of the chamber being defined by the other disk, so that as the coupling halves oscillate with respect to each other, the fluid in the displacement chambers is compressed when the oscillations are in a particular direction, and this damps the oscillation. For damping the oscillations, the displacement chamber has throttle slots, or the like, for permitting controlled exit of fluid from the chamber for damping.
The known coupling has on the circumference of the interior space of the coupling a plurality of displacement chambers of variable volume wherein a damping fluid is forced through throttle slots upon the load induced rotation of the two coupling halves. The damping effect upon rotary oscillations connected therewith is substantially constant over the angle of oscillations. In this case also, the possibility of adapting the damping direction to the angle of twist has already been considered. However, it has been found in practice that this is not sufficient in critical applications. One main problem is to obtain optimal matching of idle load and partial loads and at the same time provide good resonant behavior. Slight damping is required in idle operation, in partial and full load operation and in push operation, but high damping is needed upon passing through the resonance speed of rotation and upon change of load.
Federal Republic of Germany OS 3,322,374 (and corresponding DE-OS 33 29 420-Al) discloses a coupling in which several outer and inner lamellae are arranged between two outer side disks. Between radially inwardly and outwardly directed extensions, there are formed a plurality of displacement chambers which are limited laterally by the adjacent lamellae. Upon the load induced twisting, the volume enclosed within the displacement chamber is reduced, but the cross section of the radially active surfaces remains constant and thus the degree of damping also remains constant.
Federal Republic of Germany Patent 3,708,345, (and corresponding commonly assigned U.S. Ser. No. 07/272,698 filed Nov. 14, 1988) which does not constitute a prior art publication, discloses a coupling with inner disks which form variable displacement chambers with corresponding extensions of the outer disk. In this connection, the inner disks experience a different twist during the rotation as a result of the construction and arrangement of the flexible spring elements. In this way, the damping produced in the displacement chamber has been so improved that the displaced volume follows approximately the increase in loading and the stepwise turning of the twisting disks. This dependence is, however, still not sufficiently effective since the gaps between the disks are too large. The disks can wobble during rotation and migrate axially on the hub so that the volumes of the displacement chambers and the throttle slots continuously change their sizes. The damping can thus not be determined sufficiently precisely and is very difficult to influence since the disks are also axially flexible.